Background: The cortical thickness index (CTI) is a measure of bone quality and it correlates with the risk of proximal femoral fractures. The purpose of this study was to investigate the CTI in femoral neck, trochanteric fractures and non-fractured femora in geriatric patients and to determine whether there is a correlation between the CTI and the presence of a fracture. Methods: One hundred and fifty patients (fifty femoral neck- (FNFx), fifty trochanteric fractures (TFx) and fifty non-fractured (NFx)) with a mean age of 91 (range 80–104) years were included. Hip radiographs (antero-posterior (ap), lateral) were evaluated retrospectively. Measurements on the proximal femoral inner and outer cortices, including CTI and Dorr’s canal calcar ratio (CCR), were assessed for inter-observer reliability (ICC), differences of each fracture and correlation of parameters. Results: The mean ap CTI on the affected side was 0.43, 0.45 and 0.55 for FNFx, TFx and NFx, respectively. There was a significant difference of the ap CTI and CCR comparing the injured and healthy side for both fracture cohorts (p < 0.001). Patients with FNFx or TFx had significantly lower CTI on both sides compared to the NFx group (p < 0.05). There was no difference for CTI (p = 0.527) or CCR (p = 0.291) when comparing both sides in the NFx group. The mean inter-observer reliability was good to excellent (ICC 0.88). Conclusions: In proximal femoral fractures, the CTI and CCR are reduced compared with those in non-fractured femora. Both parameters are reliable and show a good correlation in geriatric patients. Therefore, especially for geriatric patients, the CTI and CCR may help to predict fracture risk and consult patients in daily practice.

Background/Objectives: Osteoporosis is prevalent in the elderly and increases fracture risk. Bone density is commonly assessed using dual-energy X-ray absorptiometry (DEXA). The femoral cortical thickness index (CTI) also provides indirect information for osteoporosis. It remains unclear whether there are intra-individual differences and if a correlation to fracture risk of the CTI in fractured femora results due to fracture related malrotation during X-rays. The aim of this study was to investigate the individual bilateral CTI in patients with proximal femoral fractures. Methods: A retrospective analysis of 200 surgically treated patients (100 trochanteric, 100 femoral neck fractures) was performed. Measurements included the bilateral CTI at 10 and 15 cm below the lesser trochanter. Analysis of the correlation of those examinations, in comparison to the contralateral CTI at 15 cm, and correlation of the CTI with the body mass index (BMI) and age was performed. Results: Results showed significant differences (p < 0.001) in bilateral CTIs for both fracture types at 15 cm with a strong inter-rater reliability (ICC > 0.9). There was no significant correlation between age and CTI, as well as BMI and CTI in both cohorts (p > 0.1). Sex-specific subgroup analyses revealed that females exhibited significant differences in CTI between fractured and non-fractured sides (p < 0.001). Conclusions: In conclusion, CTI, and the modified CTI at 15 cm below the lesser trochanter in fractured proximal femora, is lower compared to the non-fractured side. The femoral CTI could help in daily clinical routines and circumstances, where more detailed risk prediction tools are lacking.